Field of the Invention
The invention relates to a sheet-fed rotary printing press having at least one unit which includes an impression cylinder and an additional cylinder assigned to the impression cylinder, the impression cylinder and the additional cylinder being relatively adjustable a spaced distance from one another.
In multicolor sheet-fed rotary printing presses, downline from which a varnishing unit is disposed, the transported sheets are printed with ink only in the initial printing units during the printing operation. Downline printing and varnishing units, respectively, are in an idling mode wherein the rubber blanket cylinder and the varnish blanket cylinder, respectively, are disengaged from the printing cylinder. A small gap is formed therebetween, through which the previously printed sheets are transported. Because of the high press speed, the sheets lift away from the respective printing cylinder, so that the freshly applied ink comes into contact with the rubber blanket or varnish blanket and smears.
The published German Patent Document DE 43 18 777 C2 shows a printing unit of a sheet-fed rotary printing press, wherein devices for aiding or promoting sheet guidance are provided, in order to avoid, respectively, smearing of and damage to the freshly printed image. The provisions taken in the heretofore known devices, however, are not always effective because, for example, in a rear region of the sheet, contact of the sheet end with the rubber blanket or the varnish blanket cylinder occurs, nevertheless, when the printing is performed on stiff sheet material.